1. Field of the Invention
The present invention is directed to pumps, and, more particularly, to piezoelectric pumps having a multiplicity of waveplates electrically undulated by shear transducer action.
2. Description of Background Art
The preponderance of known piezoelectric pumps use a stack of piezoelectric elements, each element deforming with 2-dimensional extension accompanied by a thickness deformation, the latter deformations producing a mechanical stroke that is the sum of the minute strokes of each element. Extensions and thickness deformations are inseparable. A stack of thickness elements is generally bonded to a rigid support means at one end, and is bonded to a rigid moving member such as a pump piston at the opposite end. Therefore, a bonded stack of thickness elements produces a stroke that is less than the stroke produced by a stack that is not rigidly bonded at its ends because a portion of the extension stroke is inhibited. The rigid bonding also causes internal shear and tensile strains in the stack.
Thickness stacks used in pumps generally use piezoelectric material of the ferroelectric type. The ferroelectric material is polarized in the direction of the applied electric field. If a reverse electric field is applied, the polarization will be reduced, destroyed, or reversed in direction, all of which reduce the performance of the piezoelectric elements. Therefore, thickness stacks are usually operated with monopolar electric potentials. Electric drive means that provide monopolar electric signals are more complicated than bipolar electric drive means because of the need for floating power sources. A thickness stack therefore produces half the mechanical stroke that would otherwise be available if both electric drive potentials and piezoelectric deformation were bipolar.
Known piezoelectric pumps use a piston or other displacement means to move fluid wherein the displacement means generally oscillates while at least two valves prevent most of the displaced fluid from moving in a direction other than the desired one. Typical of this class of pumps is a piezoelectric fuel injector by Takahashi, U.S. Pat. No. 4,803,393 in which piezoelectric action is transmitted hydraulically by means of a diaphragm or a bellows. The life of known pumps is shortened by rubbing at contacts between seals and sliding surfaces, between displacers and cylinders, and by fatigue of valves and, if used, of flexible membrane seals.
Known piezoelectric pumps store a large portion of the circulating energy in the form of elastic deformation of the pump body and in the mechanisms attaching the displacing means to the piezoelectric actuator stack. Additional energy is stored in the piezoelectric elements in the form of electric charge. These energies are generally only restored to the pump system between portions of the pumping cycles during which useful work is performed on the fluid. Energies that are not returned to the pump system but are dissipated as mechanical heat of friction or electrical heat of resistance operate with reduced electromechanical efficiency, and suffer a shorter life because of the accompanying higher operating temperatures. The pump drive means of Mitsuyasu, U.S. Pat. No. 4,688,536, charges piezoelectric elements in electrical parallel and discharges them in a sequence through inductive-capacitive circuits. Pump action is designed to be pulsatile and abrupt as required by the application of the invention to injecting fuel.
3. Objects of the Invention
An object of the present invention is the forceful movement of fluid from an inlet to an outlet without wear due to rubbing and with few and benign life-shortening mechanisms.
Another object of the present invention is pumping of fluid with high electromechanical efficiency obtained by electrically resonant activation. A further object of the present invention is the pumping of fluid without valves.
Another object of the present invention is higher speed of actuation by the direct action of apparatus components on the medium receiving the action, without resort to intermediary structural members. Yet another object of the invention is the acceleration of fluids to very high speeds for use in electromechanical propulsion.
An additional object of the present invention is controlling any combination of fluid flow, inlet pressure, and outlet pressure by a valve action, and the maintenance of a valve state without further input of electrical power.
A further object is fluid filtering wherein the upper limit of size of passed particles is continuously controllable electrically, and the maintenance of a filter state without further input of electrical power.
Additional objects of the filtering function of the present invention is a self-rinsing filtering action and electrically controlled particle sorting.
Still another object of the present invention is emulsification of quiescently immiscible fluids such as oil and water, and the disruption of agglomerated two-phase fluids such as flocculates and biological cells.
The object of a variant emulsifier is more efficient action by superposing ultrasonic signals on the emulsifying signals. Still yet another object is electrical control of short electromagnetic waves.
Another object is electrical power generation of the pump embodiment by the transduction of fluid power to electrical energy. Another object is the modulation of an optical beam.
A further object is the imaging of x-rays by electrically figuring grazing incidence mirrors.
Another object is the application of the present invention to grinding.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.